Lpg injection with surfactant for relieving permeability blocking

ABSTRACT

Introduction of mixture of LPG and surfactant for relieving blocking of well.

United States Patent 1 Weaver et al.

LPG INJECTION WITII SURFACTANT FOR RELIEVING PERMEABILITY BLOCKING Inventors: Clarence W. Weaver, Houston;

Robert R. Scroggins, Midland, both Appl. No.: 281,599

Related U.S. Application Data Continuation of Ser. No. 87,323, Nov. 5, 1970,

abandoned.

U.S. Cl. 166/305 R, 166/304 Int. Cl E211! 43/16 Dec. 11, 1973 [58] Field of Search 339/304, 305 R [56] References Cited UNITED STATES PATENTS 2,356,254 8/1944 Lehmann, Jr. et a1 166/304 3,241,614 3/1966 Bertness 166/304 3,477,513 11/1969 Ferguson 166/304 3,718,586 2/1973 Rollo et al. 166/304 Primary Examiner-Joseph H. McGlynn Attorney-Jonathan Plaut [57] ABSTRACT 3 Claims, No Drawings 1 LPG INJECTION WITH SURFACTA'NT FOR RELIEVING PERMEA BIILITY BILOGKING This application is a co'ntinuation of Ser. No. 87,323, filed Nov. 5, 1970, and now abandoned.

BACKGROUND. or THE INVENTION This invention relates to an improved method of releasing the hydrocarbon fluids in a well'formation' into the well bore by the alleviation of a permeability block. Such blocks, which maybe causeclby the introduction of various acids into the well formation; for example, may be in the form of water wet acid fines and acidemulsion blocks or emulsions, or water oil blocks. These permeability blocks can greatly reduce the capacity of the well to produce hydrocarbon fluids in place and in many instances they have completely blocked the flow of hydrocarbon fluid'st'othe well bore.

My invention resides in a method of removing a permeability block thereby releasing productionin a hydrocarbon fluid containing formation by injecting into the blocked formation a mixture of C, and C (propane and butane) solvents further mixed with aspecial de-emulsifier and surfactant solvent, called a surfactant, all being: compatible with oilor gas producing reservoirs without causing further damage. The'particular deemulsifier and surfactant solvent'prefrred is a mixture of ethylene glycol and butyl ether, from:

about 1 percent to about 5 percent in the C;- C

mixture and preferably: from about 2 'percentito about- 3 percent, aswill bediscussedl'ater. The operation of my invention requires that the above'mixture-besoluble in reservoir crude oilor gases; When the mixture enters the well bore at sufficient pressures and rates so as not to produce fractures, the soluble solution will penetrate the formation out from the well bor'e'and clean and de-emulsify thus breaking, the permeability.

' mation, or by performing an open hole completionthrough the producing. zone: In either completion method the tubular pipe is bonded to the formation and earth by cementing, whichisa readily acceptable practice in the art. When the pipe is set' 'throughthe formation producing zone, thehydrocarbon fluids" inthe formation are provided access to the well bore by openings produced by perforating, slotting or other acceptable methods. Production tubing of a smaller diameter than the rigidly heldcasing is installedthrough the easing to a point adjacentto the hydrocarbon-containing formation.

A high gravity, low viscosity liquid (a mixture'of C, C and the surfactant), which is compatible and'soluble to the fluid in the formation, ispumped'down the tubing through the openings in one embodiment (or in another embodiment, for example, through the casing) and into the hydrocarbon-containing formation. The rate of injection and the volume of theliquid is sufiiciently maintained so that no additionalfractures to the formation matrix is experienced'inthe producing formation. The rate and volume are determinedby calcu- 21 lating the overburden pressures requiredto fracture the formation matrix andwill" vary from-wellto well.

Sufficient volume of the high viscosity de-emulsifying liquid are injected until the injected liquid reaches a point calculated to be beyond the permeability block volumes; These volumes can be readily determined by using the known quantities" of the product injected whichcausedor createdthe permeability block andthe depthof the producing formation", porosity, permeability and the like. As the mixture enters the area of the permeability block it begins to occupy the pore spaces deserted by the displaced blocking material (such as emulsion droplets). During this entry, the formation fluids-are being joined by the solvent mixture, breaking downthe bond which caused-the impermeable block.

After the injection is completed and sufficient volumes of the solventmixture are displaced into the hydrocarbon bearing formation, the well is preferably shutin for a period of about 1-2 to about 24 hours to allow the injected solvent to-further mix with the fliuds in the formation. Thus, by virtue of the solvent injection, the formation fluids willthen contain high energy, high gravity, low viscosity droplets, thereby allowing the naturalformation pressures to flow the product to the well bore atopening' of the well.

The method of well bore cleaning of permeability blocks caused by the introductionof foreign fluids such as-hydrogen chloride (HQl) and water mixtures, naturalcrud'e residue blocks and the like requires a high gravity, low viscosity, de-emulsifying solvent having a vapor pressure of not less than S'psig at F. and not more than psig at 100F. The solvent'mixture must be totally compatible andsoluble to the formation oils i and it mustbe compatible as who precipitate solids when it is mixed in the formation.

The preferred solvent mixture is a hydrocarbon in the range of about 70:30 to 50:50 ratioof C to C further mixed withapercentage ratio by volume of about 1 to 5 percent'inthetotal mixture and-preferably 2 to 3 percent compatible solvent that will act as a friction reducing agent and de-emulsifier. As stated, a mixture of ethylene glycol and butyl ether (specified gravity 0.091 and density 7.51 pound/gal.) marketed, for example, under the brand name of Corexit 7610 well stimulant (Humble) may be employed as the surfactant. The surfactant will act as a sand wetting agent and deemulsifier. The C C combination used in combination with surfactant allows (l) for the spreading of the surfactant through the formation area, (2) the provision of energy to return it, and (3) the leaching of hydrocarbonssuchas parafiin in addition to the action of the surfactant. In other words, the C C. combination works in combination with and in cooperation with the surfactant which is mixed with it. For further reference to the action of the C C mixture alone, reference should be had to US. Pat. No. 3,477,513. This method is adaptable to any hydrocarbon producing reservoir that is being limited by well bore damage from residues or permeability blocks from foreign or previous injections'and the like;

The optimum amount of the above described solvent mixture is a function of reservoir parameters and as thickness, permeability, porosity and the like, all of which are generally determined at the wellsite. The solvent mixture may be displaced by a low weight gaseous solvent, such as propane.

surfactant mixture was pumped at 1 barrel/minute-at a pressure of 2,500 pounds and displaced with 100 percent propane. 5,000 gallons of the mixture was so displaced. The well was shut in for 24 hours. It was then opened and flowed at a rate of 130 barrels a day of oil.

Although specific details have been given in the description above, it is intended that the invention only be limited by the following claims.

We claim:

1. Method of unblocking formations comprising introducing a mixture of only propane, butane, and surfactant into the formation, the surfactant comprising ethylene glycol and butyl ether and making 'up from abut 1 percent to about 5 percent of the total mixture, by volume, said mixture being introduced at a pressure sufficient to overcome the well pressure but not sufficient to fracture the formation, holding the well under said pressure, and removing said. mixture from the well with the dissolved particles from the well.

2, Method as set forth in claim 1, the surfactant having a specific gravity of about 0.9 and a density of about 7.51 pounds/gallon.

3. Method as set forth in claim 1, the propane and butane being in the range of 70:30 to :50 of the total of the two ingredients and the surfactant making up from about 2 percent to about 3 percent of the total mixture, by volume.

ll I! III UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent 3,7'77',820 Dated December 11, 1973 Inventor) Clarence W. Weaver and Robert R. Scro'gglns It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 21, "fliuds" should be -fluids-. Column 2, line 43, "specified" should be --specific Column 2, line 43 "0.091" should be .9o1--.

Signed and-sealed this 16th day of July 1974.

(SEAL) Attest:

MCCOY M. GIBSON, JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents 

2. Method as set forth in claim 1, the surfactant having a specific gravity of about 0.9 and a density of about 7.51 pounds/gallon.
 3. Method as set forth in claim 1, the propane and butane being in the range of 70:30 to 50:50 of the total of the two ingredients and the surfactant making up from about 2 percent to about 3 percent of the total mixture, by volume. 